1 files changed, 43 insertions, 0 deletions
diff --git a/lib/auth.dart b/lib/auth.dart
new file mode 100644
index 0000000..6ee8a0b
--- /dev/null
+++ b/lib/auth.dart
@@ -0,0 +1,43 @@
+import 'package:beam_messenger/data/database_helper.dart';
+
+enum AuthState { LOGGED_IN, LOGGED_OUT }
+
+abstract class AuthStateListener {
+  void onAuthStateChanged(AuthState state);
+}
+
+// A naive implementation of Observer/Subscriber Pattern. Will do for now.
+class AuthStateProvider {
+  static final AuthStateProvider _instance = new AuthStateProvider.internal();
+
+  List<AuthStateListener> _subscribers;
+
+  factory AuthStateProvider() => _instance;
+  AuthStateProvider.internal() {
+    _subscribers = new List<AuthStateListener>();
+    initState();
+  }
+
+  void initState() async {
+    var db = new DatabaseHelper();
+    var isLoggedIn = await db.isLoggedIn();
+    if (isLoggedIn)
+      notify(AuthState.LOGGED_IN);
+    else
+      notify(AuthState.LOGGED_OUT);
+  }
+
+  void subscribe(AuthStateListener listener) {
+    _subscribers.add(listener);
+  }
+
+  void dispose(AuthStateListener listener) {
+    for (var l in _subscribers) {
+      if (l == listener) _subscribers.remove(l);
+    }
+  }
+
+  void notify(AuthState state) {
+    _subscribers.forEach((AuthStateListener s) => s.onAuthStateChanged(state));
+  }
+}